The purpose of the Biostatistics/Data Management core is to develop, maintain and guarantee the integrity of the program project data base and to direct appropriate statistical analyses to address the scientific questions of the program. The specific aims of the data management and biostatistics core are: 1. to create, manage and secure the project's data base; 2. to collaborate with project scientists in the design and analysis of the component studies; and 3. to develop new statistical methodology as necessary for valid and efficient inferences about project hypotheses. The data base will be created at the Johns Hopkins Wilmer Institute and maintained on a dedicated microcomputer with tape/cartridge backup. Questionnaires will be standardized, data entry will be verified and range- checked; monthly summary reports will be distributed to investigators; backups will be made weekly and one copy housed off-site. The statistical analysis will be conducted in three stages: exploration of univariate and multivariate empirical distributions of observed variables; statistical modelling of the relationship between observed responses and explanatory variables; and formal inferences which will take account of latent variables and measurement error. The first and second steps will be performed using the statistical packages S and SAS. The final step will use the program LISREL for continuous measures but will require methodologic and computer software development more generally.